This invention relates generally to robotic apparatus, and more particularly, to robotic manipulator arms which are operated to perform a desired series of movements.
Various robot arm systems have been disclosed in the patent literature and are commercially available. Such arms invariably include a tool at their free end for moving the tool to desired spatial positions to effect some task. Prior art arms are frequently jointed or articulated so that the tool can be moved to any position in a three dimensional envelope. This envelope is commonly referred to as the working volume of the arm.
Typical prior art arms which are formed of plural joints with interconnecting sections (sometimes referred to as "links") are those whose joints are arranged so that the links can be moved to simulate movements of a human arm. Hence, robot arms frequently include a "shoulder joint" for rotating the arm about a horizontal axis, a "wrist joint" for rotating the tool holder about a horizontal or pitch axis, a "wrist joint" for rotating the pitched tool holder about an axis, etc. Motors or other actuators, e.g., solenoids, are used to effect the motion of the jointed arm sections. The operation of the motors is usually accomplished under computer control. In this regard, in state of the art systems, the robot arms are controlled by computer means which frequently include microprocessors for effecting movement of the arm to various positions within the working volume in accordance with the predetermined teachable, repeatable program. To accomplish such computer control, the joint motors frequently have associated with them encoders to provide signals indicative of the joint position. These signals are operated on by mathematical computating means in the system's microprocessors so that the exact position of the tool within the working volume is determined to insure accurate arm positioning when the joint motors are operated to move the arm to another position within the working volume.
Heretofore, the geometry of the location of the various joints of prior art robot arms has rendered the calculation of tool position a relatively complicated matter, thereby necessitating powerful processing or computer capacity to effect such calculations.
As will be appreciated by those skilled in the robotic art, the working volume of the arm is a function of the degree of mobility of the joints and the extension of links making up the arm, less the actual volume taken up by the arm itself. Needless to say, it is desirable to maximize the working volume of a robot arm, since an arm with a large working volume permits the performance of a wide range of tasks. Heretofore, prior art robot arms have not provided a sufficiently large working volume for a given size arm.